f*/.h-/*' 


[ssued  Julj  15,  1912. 


U.S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU   OF   ENTOMOLOGY  -CIRCULAR   No.  151. 

L.  O.   HOWARD.   Entomologist  and  Chief  of  Bureau. 


Till-]  GREENHOUSE  Til  IMPS. 


BY 


II.  M.  RUSSELL, 
Entomological  As s  i s taut. 


WASHINGTON  :  GOVERNMENT  PRINTING  OFFICE  :  1012 


BUREA  U  OF  ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  Chief  of  Bureau. 

C.  L.  Marlatt,  Entomologist  and  Acting  Chief  in  .  l/*«  nn  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 

W.  F.  Tastet,,  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  insect  investigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crap  insect  investigations. 

F.  M.  Webster,  in  charge  of  cereal  and  forage  insect  investigations. 

A.  L.  Quaintance,  tn  charge  of  deciduous  fruit  insect  investigations. 

E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  ofpri  venting  spread  of  moths,  fi<  Id  work. 

Roi  i  a  P.  Currie,  in  charge  of  editorial  work. 

Mabel  ColcObd,  in  charge  of  library. 

Truck  Crop  and  Stored  Product  [nsect  Investigations. 
F.  II.  Chittenden,  in  charge. 
H.  M.  Russell,  C.  H.  Popenoe,  Wm.  B.  Parker,  II.  0.  Marsh,  M.  M.  High. 

Fred  A.  Johnston,  John  E.  Graf,  entomological  assistants. 
1.  J.  Condit,  collaborator  in  California. 
P.  T.  Cole,  collaborator  in  tiilcirtiicr  Virginia. 
W.  N.  Ord,  collaborator  in  Oregon. 
Tims.  ||.  Jones,  collaborator  in  PortoRico. 
Marion  T.  Van  Horn,  Pauline  M.  Johnson,  preparators. 
ii 


Circular  No.  151. 

United  States  Department  of  Agriculture, 

BUREAU   OF  ENTOMOLOGY. 
L.  O.   HOWARD,  Entomologist  and  Chief  of  Bureau. 


THE  GREENHOUSE  THRIPS.1 

I  //.  i  lalis  Bom  I 

By  II.  M.  Russell, 
Entomological  Assistant. 

INTRODUCTION. 

The  greenhouse  thrips  has  been  the  cause  "!'  considerable  injury  to 
ornamentals  during  the  past  century,  and  where  its  presence  is  not 
suspected  or  treatment  i-  oeglected  it  will  cause  the  utter  ruin  of  cer- 
tain plain-,  in  the  greenhouse,  grown  principally  for  the  beauty  of 
their  foliage.  Likewise  in  the  more  tropical  sections  of  the  United 
States,  such  as  southern  Florida  and  southern  California,  this  insect 
causes  Lrivat  damage  to  some  outdoor-  plants. 

DESCRIPTION    AM)    I. UK    HISTORY. 

The  adult  of  this  thrips  i-  a  -mall,  active  insect  aboul  one  twenty- 
fourth  of  an  inch  in  lengt  h  and  dark  brown  in  color,  with  the  tip  of  the 
decidedly  lighter.  The  appearance  of  this  insect  is  sufficiently 
illustrated  in  figure  1  to  render  a  more  detailed  description  unneces- 
sary. Tin-  insect  feeds  on  the  foliage  of  the  plant  attacked  and 
removes  all  the  coloring  matter,  leaving  the  leaf  white  and.  in  severe 
cases  of  attack,  dead.  During  this  period  the  female  deposits  her  eggs 
(fig.  '_'.  a  within  the  leaf  tissue  and  these  hatch  in  the  greenhouse  in 
about  eight  day-.  The  larva  which  hatches  from  the  egg  is  a  minute 
white  insecl  <>(  the  shape  indicated  in  figure  _',  6  and  c.  During  1  his 
period,  which  requires  from  in  to  20  days,  varying  with  the  tempera- 
ture, the  larva'  feed  together  in  colonies  on  t he  surface  of  t he  leaf  and 
remove  i  ho  coloring  matter  in  the  same  manner  as  do  the  adults.  While 
ged  in  feeding,  the  larva  exudes  a  large  drop  of  reddish  Quid  from 

'  Fora  fuller  technlc  il  treatment  of  this  insect  sec  "The  Greenhouse  Thrips,"  Bnl.  64,  Pt.  VI,  Bur.  Km., 
V.  S.  Dept.  Apr. 

r-Cir.  151 — 12  I 


2  THE    GREENHOUSE    THKIPS. 

the  anal  end  of  the  body,  and  when  this  becomes  too  heavy  it  drops  to 
the  leaf  surface  and  dries  into  a  black  dot.  Where  the  insects  are 
numerous  these  exudations  produce  a  marked  discoloration  of  the 
foliage.  Upon  becoming  full  grown  the  larvae  change  to  the  resting 
stages — prepupa  and  pupa  (see  fig.  3) — during  which  time  they 
remain  more  or  less  motionless  among  the  feeding  young  and  take  no 
food.  These  stages  require  periods  of  about  four  to  six  days,  after 
which  the  adults  emerge.  Figure  5  shows  a  colony  of  pupse  on  a  leaf 
of  croton.     The  total  time  required  for  this  insect  from  the  time  the 


Fig.  1. — Greenhouse  thrips  I  Heliothrips  hxmorrhoidalisy.  Adult  female,  enlarged  about  50  diam- 
eters, and  greatly  enlarged  drawing  of  antenna  underneath.     (.Author's  illustration.) 

egg  is  laid  until  the  adult  emerges  ready  to  reproduce"  its  kind  is  from 
20  to  33  days,  and  as  this  insect  continues  active  in  the  greenhouse 
the  entire  year  many  generations  occur  each  year. 


OEIGIN    AND   DISTRIBUTION. 

Although  this  insect  was  first  described  from  Europe  and  is  there 
widely  distributed,  it  is  without  doubt  indigenous  to  tropical 
America.  Tt  lias  been  recorded  in  the  open  in  St.  Vincent  and  Bar- 
bados. This  insect  has  been  collected  at  Miami.  Fla.,  on  plants  in 
the  open  in  midwinter.  At  Stmt  a  Barbara,  CaL,  it  caused  consid- 
erable damage  to  ornamentals  in  one  of  the  parks  in  November. 


rip 

larva,  first  stage;  c,  larva,  full  grown. 
All  enlarged  about  40  diameters. 
(Author's  illustration.) 


THE    < .  K I  I   ffHOUS]       I  II  KIPS.  3 

These  records  of  occurrences  at  several  localities  in  the  Tropical  and 
Lower  Austral  life  zones  of  this  country  point  strongly  to  tropical 
America  as  ii-  original  home.  This  i^  further  strengthened  because 
of  its  well-known  babil  of  living  in  greenhouses,  in  many  localities, 

upon    exotic     plant--     from    the     Tropics. 

From  this  habil  it  bas  become  widely  dis- 
tributed in  Europe  and  North  America. 
1  ii  Europe  il  i-  recorded  from  England, 
Germany,  Austria,  Russia,  Finland, 
France,  Spain,  and  Italy.  Jt  is  also 
known  to  occur  in  Australia  and  the 
I  law  aiian  Islands. 

In  this  country  it  is  recorded  from 
Massachusetts,  from  several  places  in 
Michigan,  and  from  Washington,  D.  ('.. 
Florida,  and  California.  It  bas  been  col- 
lected in  Iowa  and  Pennsylvania  and  in 
the  Barbados  and  the  island  of  St.  Vin- 
cent, British  Wesl   Indie-. 

Because  of  the  fad  that  it  bas  been  col- 
lected in  such  widely  distanl  places  in  all 
sections  of  thecounl  r\ ,  we  can  safely  saj  that  Helioihripsha  morrhoidalis 
is  generally  distributed  in  greenhouses  throughout  the  United  Mate-. 

\  Vinti:    AND    EXTENT   OF    IX.UKY. 

Tin1  damage  caused  by  the  greenhouse  thrips  to  ornamental  plants 

i-  confined  to  the  foliage  entirely. 

in  SO  far  a-  I  he  aul  hor  is  aw  are,  for 
he  knOWS  of  QO  recorded   injury  to 

the  blossoms  of  theplantsnorhashe 

noticed  any.  The  damage  to  fruits 
i-  divided  between  injury  to  the 
foliage  and  t  o  the  fruit  itself.  In- 
jury effected  by  the  thrips  is  due  to 
the  method  of  feeding  on  the  plants. 
Both  adults  and  larvae  obtain  their 
food  by  puncturing  the  epidermis 
of  the  leaf  or  fruit  w  ith  their  sharp 
moul bparts,1  and  after  lacerat big 
the  tissue  they  suck  out  the  vege- 
table matter  ami  plant  juice-  :ii 
the  point  of  attack.  The  inseel 
then  at  tack-  t  he  leaf  or  fruit  in  a  new  place,  50  that  in  time  it  becomes 
full  of  tiny  pale  -put-  where  the  vegetable  matter  has  been  exl  ract  ed. 

>  1  Dr  structure  of  mouthpaii  Thrips,"  by  Dudley  Moultoti,  Bui.  08,   Pari  I,  Bur. 

Ent.,  V.  8.  I1  .  1907. 


eenhouse  thri|>s:  Prepupa  on  the  left 
and  pupa  on  the  right.  Enlarged  about  40  >li- 
amcters.     (Author's  illustration.) 


THE    GREENHOUSE    THRIPS. 


In  the  case  of  infested  plants,  injury  is  noticed  first  to  the  older 
leaves   and  gradually,   as  these  become   badly  infested,   the  injury 


FlG.  4.— Portion  of  leaf  of  crolou  magnified  to  show  pupa-  of  greenhouse  thrips.     ('  »  Iginal.  I 

spreads  until  the  young  leaves  are  attacked,  soon  after  unfolding. 
The  infested  leaves  first  show  injury  on    the   underside,  where  the 


GR]  ENH0US1      I  BRIPS. 


epidermis  appears  full  of  minute  white  spots.  As  attack  continues 
the  spots  become  more  numerous  and  unite,  forming  blotches  where 
the  leaf  is  damaged.     Figures   I  and  5  shows  leaves  of  croton  badly 


/.'             ^^p*^^-<<flft. 

jT^? 

&:J&i    "-^l 

KgW?-A 

^"SfcSM- 

5w^l    / 

W  ■  1 1 

.jy^^fr 

wis        ^ 

\ 

* 

Fio.  5. — Croton  leavi  .  showii      blea  i.        I  black  and  brown  spots  due  to  reeding  of  the  greenhouse 

thrips.    (Original.) 

injured  by  this  insect.  The  injur}  then  becomes  apparent  from  the 
surface  and  develops  a  twisted  and  distorted  aspect  between  the 
lateral   veins,   and   is   finally   evidenced    by   wilted   and  dead   area- 


THE    GREENHOUSE    THRIPS. 


Fig.  6. — Croton  plant  showing  healthy  appearance,  Washington,  D.C.,  December,  1911.    (Original.) 


I  ill     GRI  l  N  ih>i  SE    I  HRTPS. 


around  the  edges  of  the  leaf. 
In  severe  attacks  the  insects 
-prcad  1o  the  upper  surface  of 
the  leaves,  and  in  a  shorl  time 
this  as  well  as  the  underside  is 
nearly  devoid  of  color.  Both 
side-  become  thickly  covered 
\\  ith  minute  drops  of  reddish 
fluid  voided  by  the  thrips, 
which  gradually  change  to 
black.  As  the  attack  con- 
tinues, the  leaves  become  limp 
and  yellow  and  event  ually  drop 
off,  so  that  the  plants  that  are 
not  treated  to  prevent  injury  ill 
many  cases  lose  their  entire  foli- 
age. Figure  6  show-  normal 
croton  and  figure  7  croton  to- 
tally defoliated  by  the  adults 
of  this  insect. 

This  inseel  injures  plants  in 
tw  0  w  ays:  Firsl ,  a  serious  drain 
on  the  v  itality  of  the  plant  is 
produced  by  the  feeding  of  thou- 
sands of  thrips,  mp  that  the 
grow  th  is  seriously  checked  and 
in  neglected  cases  causes   the 

death  of  the  plant.      Second,  it 

destroys  the  beauty  of  the 
plants  for  ornament  by  event- 
ually despoiling  them  of  I  heir 
foliage. 

I  n  southern  Florida  thisinseel 
attacks  the  mango  and  alligator 
pear  and  causes  greal  injury  \>y 
feeding  on  the  foliage  and  it 
may  also  cause  injury  by  feed- 
ing on  the  young  I'm  it  and  scar- 
ring it  to  a  large  extent. 

At  Santa  Barbara,  Cal.,  this 
inseel  occasionally  becomes  so 
abundant  on  orange  t  rees  as  to 
ruin  the  fruit  and  cause  the  en- 
tire foliage  to  drop.  Theguava 
indusl  ry  t  here  has  also  suffered 
se\  erely  from  this  inseel . 


Fig.  7.— Croton  plant  totally  defoliated  by  ihcRrecn- 
bington,  D.i  , ,  1912. 

Inal.) 


b  THE   GREENHOUSE    THRIPS. 

FOOD    PLANTS. 

The  greenhouse  thrips  feeds  on  a  large  number  of  ornamental 
plants.  In  tins  country  it  has  been  recorded  as  feeding  on  liliaceous 
plants,  azalea,  PeUea  liastata,  aspidium,  croton,  dahlia,  phlox,  ver- 
bena, pink,  ferns,  vines,  cherry  laurel  (Prunus  caroliniana) ,  laures- 
tina,  palms,  Ficus,  and  fuchsia.  In  California  it  has  been  found  on 
raspberry,  guava  (Psidium  guajava),  and  orange.  Tins  thrips 
damages  the  mango  {Mangifera  indica),  alligator  pear  (Persea  gra- 
tissima),  and  maple  in  Florida,  and  has  been  recorded  from  St.  Vin- 
cent and  the  Barbados  on  cacao  (Theobroma  cacao),  kola,  and  the  date 
palm  (Phoenix  dactylifera) .  In  Europe  this  thrips  has  been  recorded 
as  preying  upon  serides,  azalea,  begonia,  camarotes,  cattleya,  crinums, 
dendrobium,  eucharis,  Ficus,  grape,  lselia,  lefortia,  marcintacia, 
pancratium,  phalenopsis,  banana,  and  viburnum.  In  Australia  it  is 
recorded  as  occurring  on  different  species  of  eucalyptus. 

REMEDIES. 

For  the  treatment  of  tins  pest  there  are  a  number  of  good  remedies. 
The  question  as  to  the  best  method  to  employ  depends  upon  the  size 
of  the  greenhouse  infested  and  upon  the  experience  of  the  person 
engaged  in  treating  the  insect. 

Fumigation  with  nicotine  papers. — Any  of  the  standard  fumigating 
papers  will  give  good  results  against  tins  pest  if  they  are  strictly  fresh 
and  kept  tightly  sealed.  Fumigation  should  be  done  at  night  in  a 
moist  atmosphere,  and  the  papers  should  be  used  at  the  rate  of  about 
2  sheets  for  eveiy  1,000  cubic  feet  of  space.  Early  in  the  morning 
the  house  should  be  opened  and  thoroughly  aired. 

Fumigation  with  nicotine  liquid  extracts. — Liquid  extracts  of  nico- 
tine offer  one  df  the  best  methods  of  greenhouse  fumigation  and 
against  tins  pest  are  very  successful.  Those  made  up  of  40  per  cent 
nicotine  should  be  used  at  the  rate  of  1  ounce  to  eveiy  1,000  cubic 
feet  of  space  and  the  weaker  solutions  at  greater  strengths.  The 
preparation  should  be  evaporated  over  small  lamps  or  stoves,  and 
to  prevent  scorching  should  be  diluted  with  water,  approximately 
two-thirds.  Fumigation  should  he  carried  on  at  night  in  a  moist 
atmosphere,  and  the  greenhouse  should  remain  closed  all  night. 

Fumigation  with  hydrocyanic-acid  gas.1 — When  fumigating  with 
hydrocyanic-acid  gas  great  care  should  he  taken,  as  this  gas  is  fatal 
to  all  animal  life.  The  work  must  he  conducted  at  night,  and  the 
plants  should  have  dry  foliage.  In  treating  this  insect,  use  from  0.01 
to  0.05  gram  of  potassium  cyanid  per  cubic  foot  for  from  two  hours 
to  all  night,  the  strength  and  length  of  exposure  varying  according 
to  the  tightness  of  the  house  and  the  kind  of  plants  that  are  being 

1  For  complete  directions  for  the  use  of  hydrocyanic-acid  gas,  see  Cirs.  37  and  57,  Bur.  Ent.,  U.S.  Dept.  Agr. 


l  in:  GRE1  N  KOUS]     THRIPS.  9 

treated,  as  there  is  considerable  difference  between  various  plants  in 
their  resisting  power  to  this  gas. 

Spraying   with    nicotim    liquids.    -Nicotine   extracts   diluted    with 
water,  if  carefully  applied  to  plants,  will  kill  large  numbers  of  the 
greenhouse  thrips,  bul  thegreal  objection  is  thai  many  of  the  in 
are  not  hit  by  the  spray,  and  therefore  the  plants  become  reinfe  ted 
in  a  short  time. 

Spraying  with  kerosem  emulsion?  It  is  quite  possible  that  kerosene- 
emulsion  -ptay  will  be  effective  against  the  greenhouse  thrips  when 
used  at  the  strength  of  1  part  of  stock  to  10  pan-  of  water,  and  it 
costs  considerably  less  and  is  more  readily  obtained  than  the  nicotine 
preparations.  It  should  be  very  carefully  prepared  and  used  experi- 
mentally at  first  until  the  effect  on  the  foliage  of  the  different  plants 
is  noted.  ( 'are  should  also  be  taken  to  prevent  quantities  of  emulsion 
from  collecting  around  the  roots. 

Water  spray.  Frequent  treatment  with  a  still'  spray  of  water  from 
a  garden  hose  or  syringe  will  tend  to  keep  tins  insed  down,  bul  unless 
there  are  only  a  few  plant-  it  would  he  better  to  use  one  of  the  other 
remedies. 

Any  treatment  For  this  insect  should  be  repeated  in  from  7  to  10 
day-  to  destroy  the  young  larvie  that  have  hatched  from  the  e<_r'_r-. 
This  should  be  sufficient,  but  it  may  be  besl  to  give  a  third  treatmenl 
in  another  w  cek  or  two. 

Treatment  of  trees  in  th  open. — In  the  case  of  injury  to  the  various 
subtropical  fruits  it  is  recommended  to  spray  the  foliage  thoroughly 
with  a  nicotine  spray.  A  tobacco  extract  of  2\  per  cent  of  nicotine 
sulphate,  diluted  at  the  rate  of  1  part  to  (it)  parts  in  a  6  per  cent 
distillate-oil  emulsion,  bas  given  such  good  results  againsl  the  pear 
thrips  that  this  treatment  should  be  tried.2 

Approved : 

.1  wii  -  Wilson, 

Seen  tary  of .  igricultun  . 

\\  ashing  roN,  D.  ( '..  April  19,  191 .'. 

i  For  the  method  of  making  emulsioi  Bulletin  127,  or  Cir.  80,  Bur.  Ent.,TJ.S.  Dept.  \-.t. 

>  Full  directions  for  mixing  this  spray  are  given  in  Cir.  131,  Bur.  Km..  I*.  .-.  Dept.  \ 


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